1. Field of the Invention
The present invention relates to a nail-shaped fastening element having a stem, and a head provided at one end of the stem and projecting radially beyond the stem, with the stem tapering at its other, free end toward a tip and having a spherical, first section extending from the tip in a direction toward the head, and a second section adjoining the first section.
2. Description of the Prior Art
Nail-shaped fastening elements are used for securing constructional parts to hard constructional components formed, e.g., of steel, concrete and stone. The nail-shaped fastening elements are driven into the constructional components with explosive powder-actuated setting tools. A nail-shaped fastening element is disclosed, e.g., in German Publication DE 1 575 152. The disclosed fastening element has a stem at one end of which, there is provided a head the outer contour of which has an outer thread. The stem tapers toward a tip at its other, free end. The stem has, starting from the tip, two sections arranged one after another, with the first section having a spherical shape and widening in a direction toward the head. The second section is formed as a conical section which likewise widens toward the head. The largest diameter of the first section is equal to the smallest diameter of the second section. The inclination angle of the second, conical section amounts to 3°. The length of the second conical section, which is measured in the direction parallel to the longitudinal extent of the fastening element, is rather large. Therefore, for driving the fastening element, which is disclosed in DE-1 575 152, a very high drive energy is required as the second section should displace sidewise a large amount of the material of the constructional component.
Accordingly, an object of the present invention is to provide a nail-shaped fastening element that can be economically produced, has a short length, and permits to obtain an approximately the same holding force as the known fastening element and, at the same time, requires less driving energy for driving it into the constructional component than the known fastening element.